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  • Are You Killing Your Batteries Part 2.

    Catchy title but if you use Lead Acid Batteries and use Solar to charge them, you are part of the 90% population killing your batteries. Not really your fault because you are doing what the manufactures are telling you to do. It is what they are not telling you that is killing your batteries. The Killer is Deficient Charging. The guilty party is Solar and Solar Charge Controllers.

    Every Charge Controller on the market uses what is known as 3-Stage Charging algorithm, and the three stages are Bulk, Absorb, and Float. It is a good proven algorithm and works great if you use a commercial AC Powered Charger. However it does not work with Solar in 90% of the applications. The problem is TIME, and with Solar you do not have time to fully charge your batteries.

    Here is the problem. To fully charge a Lead Acid battery requires you to apply a Bulk/Absorb charge of C/12 to C/8 and up to C/4 or little higher with some AGM batteries. Ideal model is C/10. So if you are using a 100 Amp battery you would apply 10 amps until the battery voltages reaches the Bulk/Absorb voltage set point of 14.4 volts. At 14.4 volts is the beginning of the Absorb stage. Absorb stage last until Charge Current tapers down to about 1 to 3% of C. On a 100 AH battery would be 1 to 3 amps. Once that point is reached, you lower the voltage to FLOAT of 13.2 to 13.8 volts depending on the Lead Acid battery type. Float keeps the battery 100% fully charged and allows the panels to supply the load with power.

    So what is the problem with solar? Simple it takes 6 to 12 hours to saturate the battery in Absorb mode. There are not enough sun light hours in the day to complete the cycle fully. On Solar Charge Controllers Absorb is a timed event. Absorb is not a timed event. Absorb is finished when charge current taper off to 1 to 3% of C. When your battery reaches Absorb set point voltage is only 70 to 80% fully charged. It is going to take another 6 to 12 hours to get to 100%. No problem if you have a commercial AC battery charger.

    So here is the saving grace for most of you if your charge controller allows you to set your own Bulk/Absorb/Float charge voltage. There is more than one way to charge a Lead Acid Battery or any battery for that matter except NiCd and NiMh. Turn the voltage up. It is called SPEED CHARGING. You apply a Constant Current until the battery Voltage reaches 14.8 to 16 volt set point on a 12 volt battery. As soon as the battery reaches set point, it is fully charged. There is no Absorb time involved. You force your Charge Controller to stay in Constant Current until fully charged. There is no slow time waiting for Absorb.It is as fast as physically possible.

    So what is the down side? Your battery is going to use more water, and corrosion will eventually do your battery in. However you are choosing between the lessor of two evils of Sulfating or Corrosion. You have to pick which one. Sulfating comes much sooner than a Corrosion death, and Sulfating always leaves you short on power.

    Of course there is another way. Any Off-Grid applications require a Generator or Alternate source of power. There will be cloudy spells, and all Lead Acid Batteries need an Equalization charge every 30 days or so no matter what the application is. Get a few cloudy days, and you go dark waiting for the sun to return plus another couple of days waiting to recharge. Equalization charges take up to 24 hours to complete and no solar system can EQ a battery or fully charge a battery in most applications.

    Now some of you might be thinking why not just use more panel wattage thus a higher and faster charge rate? Good question, but there becomes a point or brick wall in which no time is gained. Sure you will get to Absorb stage sooner, but Absorb takes longer. Example if you charge at C/8 the max recommended rate you hit Absorb at roughly 80% SOC. Increase the rate to C/6 and you hit Absorb at 60% SOC and double your absorb time. That Is just the physics involved of Ohms Law and the batteries resistance you cannot change. You have to know how to work with it. On the Flip side and what utilities and emergency power operations do is use Float Chargers. They set the voltage to 13.2 to 13.8 volts and leave it there. Takes longer, up to 24 hours, but the battery sits there at 100% SOC until used with no corrosion or sulfated plates. That is why their batteries last 10 years. That option is available to some of you like week end warriors in you cabins and some other specialized applications. But you still need that alternate source of power for EQ charge and extended stays.

    So what voltage is correct? You have to figure that out with your battery hydrometer. At the end of each day, check the specific gravity. Start at 14.8 volts, and if specific gravity is low, raise the voltage to 14.9 and so on until you reach full charge. If you smell a rotten egg, batteries are fizzing, and hydrometer is above full charge, lower the voltage. Very doubtful you will ever find an over charged condition on solar. You will most likely find there is no voltage high enough which tells you your system is under sized which most of you have.

    Battery manufactures are now changing charge recommendations. Reason is Solar and the vast amount of warranty claims. Root cause is undercharged batteries. Companies like Trojan have done away with 3-Stage Algorithms all together. Charge to 2.47 vpc (14.82 volts) and Float at 2.25 vpc or 13.5 volts. That is where you need to start and go from there.
    Last edited by Sunking; 05-30-2017, 04:47 PM.
    MSEE, PE

  • #2
    Sensij Absorb phase is determined by three variables.

    1. Resistance of the battery, which you have no control, it is what it is.
    2. Charge Current which is determined by the panel wattage and battery SOC OCV
    3. Voltage you select.

    If you use a higher charge rate say from C/10 to C/5 or 10 amps to 20 amps on a 100 AH battery. you arrive at the Absorb voltage sooner, but will significantly increase the Absorb time if you charge at the higher rate. That is just the function of higher current flowing through the battery fixed resistance.

    What I am saying is you move the Set Point Voltage higher so when you reach the set point, the OCV voltage of the battery is at 100% SOC rather than 60 to 80% SOC. Just work th emath a couple of times and you will see what I am talking about.

    A fully charged 12 volt battery is saturated at 14.4 volts when both charger and battery OCV are equal which means no current. If you have say a 10 amp charger and battery resistance = .01 Ohms, Absorb starts when the battery OCV = 14.3 volts and charge current starts to taper of as the battery voltage slowing goes up to 14.4. That is a painfully slow process. If I set the voltage to 14.5 volts, now the charger will not taper until the battery OCV is 14.4 volts OCV which is fully saturated and 100% SOC in a much faster time.

    The difference is significant. Example using the 100 AH battery with a .01 Ohm resistance charged with a 10 amp charger from fully discharged. One set to 14.4 volts and one set to 14.5 volts. The battery with the charger set to 14.5 volts will be fully charged in 12 hours. The battery with the charger set to 14.4 volts will take 20 hours. Both batteries will have had the same 120 AH pumped in.
    Last edited by Sunking; 05-30-2017, 07:43 PM.
    MSEE, PE

    Comment


    • #3
      Glad I came across this thread. Definitely learning a lot from here.

      Comment


      • #4
        Yes I think I am learning a lot we will see. I have 6 x 370W Silfab panels. 2 x EPEVER 4210 AN 40A CC's. 3 panels paralleled to each CC. CC's paralleled to the battery bank. Bank is 8 flooded lead acid golf-cart batts - 24v x 400ah.
        Battery Bank:
        4 x 6v batteries 200ah series strings (24v x 200ah) then paralleled the 2 strings for 24v x 400ah.

        Sunking you said most of us were undersized system. As a novice I did my best to size my system but most of that was based on what appliances I was running, not on how best to match panels with batteries. Does my system shortchange itself? I don't know what you meant by UNDERSIZE...too few panels, too few batteries?

        I barely understand what the CC's are doing with 3-phase charging (I was hoping they would be a much better battery minder than ME) but you are saying it is probably best if I override the controls and chart my own course. I just got my system installed and running just in time for shortest days of the year - December in Wisconsin. On Sunny days it seems to charge to 100% SOC in just a couple hours... then goes to float...but by the time the sun goes down (with hardly any draw on the inverter) the SOC % drops precipitously and is back to 50% or less by morning.
        Last edited by Wiscy; 12-17-2018, 02:59 PM.

        Comment


        • #5
          I'm not Sunking, but I'll reply to you Wiscy.
          First most of what is sold as "state of charge meters" are bogus. The ones that work, require you to install a shunt, program the size of the battery and it's efficency, and then after a couple fulll charges to calibrate it, it can come pretty close, measuring inflow and outflow.

          As to the SCO % dropping overnight, it's likely batteries are sulfated. Winter hours, you need to use a generator in the mornings a couple times a week, to bulk the batteries up, and then let the solar top them off from 10am-2pm

          Charging is in 3 stage (not phases) Bulk, where you set a voltage, and allow the battery to take as much power as it can safely inhale. Absorb, where the battery reaches the Bulk voltage, and then over the course of at least 2 hours, the amps decrease, finally FLOAT, where the last 10% of charge happens, slowly putting power in till the battery is full
          Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
          || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
          || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

          solar: http://tinyurl.com/LMR-Solar
          gen: http://tinyurl.com/LMR-Lister

          Comment


          • #6
            Thank you Mike. I will try to process what your take on the stages are. Absorb is the most mysterious, I can't tell from Sunking or your description what decreases the amps or how that is set or performed. Certainly my CC software and manual don't explain how to do that. Setting my own points and turning off the defaults on my CC will definitely put me off all the automatic things it does to keep CC and Battery safe. And I have to get it right or I will do more damage.

            The CC software and owners manual seem to use slightly different terminology and have Boost and Constant thrown into the mix. Then just when you need it to make sense, the Language Barrier pops up and their point is murky. "At this time The Same will be the same" for example. I can never tell when I am entering configuration info if it wants one battery measurement or the entire bank.

            It seems very hard to think my batteries are sulfated. They are "brand new" with 2018 born on dates. I bought them in july. I was delayed in getting them hooked up to anything because my panels and CCs and other wiring didn't come together as fast as I hoped. I bought a very cheap 24v charger in September but it did almost nothing to charge the whole bank....but my voltage readings were good and all the batteries singly tested at 6v + . The CHarger was too small, but it never read below 52% and got up to 65%. I got three panels hooked up a month ago and charging...then the last 3 panels about a week ago. I guess the waiting could have ruined them. I am clueless but they do have a 1 yr "replace for any reason" warranty.
            Last edited by Wiscy; 12-17-2018, 04:38 PM.

            Comment


            • #7
              Originally posted by Wiscy View Post
              Yes I think I am learning a lot we will see. I have 6 x 370W Silfab panels. 2 x EPEVER 4210 AN 40A CC's. 3 panels paralleled to each CC. CC's paralleled to the battery bank. Bank is 8 flooded lead acid golf-cart batts - 24v x 400ah.
              Battery Bank:
              4 x 6v batteries 200ah series strings (24v x 200ah) then paralleled the 2 strings for 24v x 400ah.......
              I think you don't have enough voltage for the controller to properly work.
              What is the Vmp of your panels ??
              What is the max save input voltage of your charge controllers ?
              What is the Voc of your panels ??

              Generally to charge a 24V battery, you need about 50 -60V from the panels into a MPPT controller, and will have to put 2 panels in series, if that voltage does not exceed the Max volt of the controller.

              Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
              || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
              || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

              solar: http://tinyurl.com/LMR-Solar
              gen: http://tinyurl.com/LMR-Lister

              Comment


              • #8
                I believe each CC has 100V max.
                They told me I had to parallel 3 panels to each CC.
                Would have been nice if they had said something about 50-60V input needed. I tried and tried to buy the right stuff and not make such a mistake, but that simple sentence you just said....you need 50-60V to impact a 24V bank ....I never came across that info and I spent months planning.

                Electrical Specifications SILFAB SLG M 370

                Module Power (Pmax) Wp 370

                Maximum power voltage (Vpmax) V 39.6

                Maximum power current (Ipmax) A 9.35

                Open circuit voltage (Voc) V 48.2

                Short circuit current (Isc) A 9.93

                Module efficiency % 19.0

                Maximum system voltage (VDC) V 1000

                Series fuse rating
                A 15
                Power Tolerance Wp -0/+5
                Measurement conditions: STC 1000 W/m2
                Attached Files

                Comment


                • #9
                  sadly, your panels are high voltage, and cannot be wired in series, which will be very close to the kill voltage of the controllers. At 39.6V, the controller may have a hard time charging the batteries fully.
                  Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                  || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                  || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                  solar: http://tinyurl.com/LMR-Solar
                  gen: http://tinyurl.com/LMR-Lister

                  Comment


                  • #10
                    so maybe a different controller would be the simplest or cheapest change. If I go to a 36v battery I have to get a different inverter. If 50-60V are needed for a 24V bank, does a 36v batt bank require fewer or more volts than a 24V bank? And a 48v bank? I could add some batteries or reconfigure them.

                    Comment


                    • #11
                      Your solar is 2,220 watts and through a MPPT controller at 24V roughly 80A. So you will need 2 cheap 40A controllers or one expensive controller.

                      There are 2 expensive, high amp controllers I can recommend :
                      Midnight Classic 150
                      Magnum Energy PT-100

                      Use a sizing tool from the Controller Mfg to determine the optimum array configuration

                      http://www.midnitesolar.com/sizingTool/index.php
                      https://www.magnum-dimensions.com/re...rge-controller


                      Note that at cold temps, 2 panels in series produces:
                      VOC Open Circuit Voltage at -30

                      Another good 60A controller that would occasionally limit your charge amps to 60A
                      Morningstar MPPT-60
                      Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                      || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                      || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                      solar: http://tinyurl.com/LMR-Solar
                      gen: http://tinyurl.com/LMR-Lister

                      Comment


                      • #12
                        Thanks for the links and info. Mike I appreciate your time and coaching.
                        I thought I DID go the 2 cheap controllers route.

                        I found this on another thread Sunking said:
                        For a 24 volt system the panel at max power rating needs to be 32 to 36 volts.
                        Roughly 16 to 18 volts for every 12 volts of battery.

                        However that rule only applies if you are using a standard PWM or shunt regulator. Using that type of regulator you will loose 30% minimum of the power from the panels.

                        However with a MPPT controller those voltage rules do not apply. They still need to be at least 36 volts, but you can go as high as around 120 volts to take advantage of wiring loss efficiency at the higher voltages. At higher voltage you use less current for a given power.
                        If you say my panels need 50V to 60V to charge my 24V battery bank, and my 3 panels in parallel to one controller produce 39V - How am I to reconcile that with the quote above?

                        Comment


                        • #13
                          I still would like some opinions on how much panel/battery I have. Is my battery bank likely to be able to store most of the power I can create? Or am I way over on one or the other?

                          Also, you can see my two attachments - 2 real-time screengrabs of my two controllers via the proprietary software. You can see my Solar Volts are up in the 40s which seems odd from a 39V array. Perhaps cold or cloud flare? OR the software isn't reading things right or I have something wired wrong.
                          Attached Files

                          Comment


                          • #14
                            Originally posted by Wiscy View Post
                            Thanks for the links and info. Mike I appreciate your time and coaching.
                            .......If you say my panels need 50V to 60V to charge my 24V battery bank, and my 3 panels in parallel to one controller produce 39V - How am I to reconcile that with the quote above?
                            You got the wrong controllers and the wrong panels. Figure out which is easier to replace. Can you return them ? Make sure the components are compatible with each other.

                            With one panel 39.6v, on a hot day, you cannot expect to generate enough voltage to charge the batteries through a MPPT controller. A PWM controller would work with your panels in parallel, you would loose some system power

                            39.6v - 29V = 10.6v x 9.35A = 99.11 watts loss per panel due to voltage mismatch. You will still get 9A per panel, but the difference of panel voltage and battery charge voltage, you loose some power.


                            Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                            || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                            || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                            solar: http://tinyurl.com/LMR-Solar
                            gen: http://tinyurl.com/LMR-Lister

                            Comment


                            • #15
                              I have the wrong panels AND the wrong controller? How can that be? Surely only ONE element needs altering, not both.

                              Make sure the components are compatible with each other? How? When I came here 9 months ago and 6 months ago you ran me off the comments board both times telling me to go read Solar for Dummies twice. Didn't answer my question either time. Now, I know I am asking for help, nobody HAS to provide it to me....and I appreciate any good faith attempt to set me straight. Since it was basically the same screed from you both times, I thought maybe it was a canned rant you used to shame people. Not sure why you want to do that, but hey. Whatever turns your crank. When you are Senior on a board, it is pretty easy I guess.

                              I had already read Solar for Dummies once. It was the least helpful of thousands of things I read. Some help from you then would have gone a long way in me ordering the proper stuff. Instead I just had to wade into the confusion once again and do the best I could. I don't know if you are the only live body left on this forum, but I have run into you like a brick wall all the 3 times I have tried. This last time I had finally got all the parts, pieces, and wiring together and now I am trying to make what I have work. I did my best. For some reason you didn't just attack me on this 3rd attempt....so I was hoping to learn something. You did avoid the humiliation stage this time, not sure why.
                              Did you just march into your solar and alternative energy projects and hit home runs everytime?

                              I tried doing the research, spent 2 yrs trying to fix a place and planned it out. Spent just over $3000. Just because I am not a wizard in this realm doesn't mean I am an idiot. I fix all my own cars, computers, networking, plumbing, and everything else that ever sprang up around a modern house. This particular field of endeavor happens to be the MOST COMPLICATED thing I have ever tackled and I am proud of what I got accomplished.

                              If there is an Achilles heel in my system or my knowledge....so be it. I tried hard and put in countless hours. I don't need chastising and ridicule. When I bought the panels nobody said there were all these limitations or compatibility issues. When I bought the controllers, I told them what panels I had and they told me what controller(s) would work. When I came here asking for help I was humiliated. You told me to give up and get a Pro.
                              No Pro installer nearby (I quoted 3 of them) wanted anything to do with a battery system. Grid Tie only. They don't understand batteries, don't want to be on the hook for them or answer user's ongoing questions about them. They want to be done and never hear from you again. I am a complete DIY er, but I dropped my guard and was willing to hire and pay a pro. I realized this wasn't something I was going to be able to learn about completely before embarking....like many of my DIY conquests. But all I got was the runaround due to batteries and not being Grid Tied.

                              So, I will go forth and make sure all my components are compatible with each other....using an abacus and a divining rod. I see people here on these forums trying to run 24v systems with 12v equipment or having a jumper cable between 2 controllers and they didn't get treated like that. If you think this site should only have Pros batting around ideas, then maybe there should be a banner saying that.

                              You quoted my 24v charging requirements above, but didn't answer it. I asked some pointed questions and you didn't answer them. Just told me everything I have is wrong.
                              I will be trying a different forum.
                              Last edited by Wiscy; 12-19-2018, 11:27 AM.

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